Has anyone got any idea how to get the non drive side crank arm off on a BBright crankset on a cervelo S5 team. I have a 53-39 crankset with longer arms I want to install but I can't get the old one off I have the bolt and lock nut undone but the crank seem to be an interference fit and wont budge

warthog1 wrote:I have a 53-39 crankset with longer arms I want to install...

What was really interesting, however, was that, while peak power was not different, the time required to achieve peak power was much lower with the 170 mm (2.57 s) than the 175 mm (3.29 s) cranks.

This has significant practical applications. The shorter cranks permitted you to generate high power outputs faster. This ability is critical in closing a gap, accelerating in a sprint, and also laying out that massive and quick burst of power to get you over an obstacle on the trail or out of a turn in cyclocross.

warthog1 wrote:I have a 53-39 crankset with longer arms I want to install...

What was really interesting, however, was that, while peak power was not different, the time required to achieve peak power was much lower with the 170 mm (2.57 s) than the 175 mm (3.29 s) cranks.

This has significant practical applications. The shorter cranks permitted you to generate high power outputs faster. This ability is critical in closing a gap, accelerating in a sprint, and also laying out that massive and quick burst of power to get you over an obstacle on the trail or out of a turn in cyclocross.

Yes but I dont sprint well. Long arms are better for tt'ing and climbing IME, as you already know you S stirrer

Went to the lbs for some cables and you leave what I thought was the lock ring in place and this acts as a crank arm extractor as you undo the retaining bolt. D'oh Nice bloke to let me know, he even demonstrated on one of the shop bikes

Right side: All the BB's sealing parts (I think there's a gray plastic "washer" designed to mate with the rubber seal in the black plastic cup), then the crank's ~11mm spacer. Nothing else on the right side.

Left side: All the BB's sealing parts, plus the crank's wave washer and as many thin (often clear plastic) spacers as necessary to get the wave compressed but not flat wen the crank bolt is fully torqued. I usually have to take it apart a few times to get the number of spacers right.

Have the wave washer from the old crankset but will have to get some plastic spacer washers as neither came with the crankset.

I didn't like the way the compact shifts, and shorter crank arms suck

bbright is bbwrong by the way, what a shitzen system compared to normal external bearing cups Wasted most of the day on the POS and its still not done.

warthog1 wrote:I didn't like the way the compact shifts, and shorter crank arms suck

Well as counter intuitive as it is, if I was riding a lot of hills (and could still maintain cadence in bottom gear) I would get a standard too, as bigger chainrings are more efficient. Since I can do my current rides in the big ring, the inner ring is just there for when road/path circumstances force me to go slow.

As you know, longer cranks are just another form of gearing. Since ideal leg speed appears to stay the same, the cadence gets lower. I've also found it better for consistency and torque in the past when MTBs only came with 175s. Back then a 28 on the front was the smallest chainring and 28 on the back was the largest sprocket. The first thing we would do is fit a 24 chainring. None of us thought of shorter cranks then.

With ITT, I suppose you've weighed up the limitation longer cranks pose in how low you can go. Other than that, they pose slightly more aero drag. Reminds me of this guy.

“I use short cranks, 165mm, which is also against current thinking — people say you should have cranks matched to your leg length. My theory is that it is lighter, stiffer and more aero, and it operates your legs over the more efficient portion of the stroke, so you can optimise your saddle height.”

As for the spacers, if you can't get the exact size spacer you want, you can sand one down (a bit) on a smooth piece of concrete. I know a guy who does this to shims for his engine cam lifters. He says it sames him time and money sourcing the correct shim. He is an experienced engine builder with his main hobbies being engines and motorcycles.

One thing I like about Shimano external cranks is the ability to fine tune the pressure on the bearings just with the hand tightened screw-adjuster (thingy). I think it allows an easy and accurate way of getting the preload as light as possible without rattling, which should reduce drag and wear. It seems many are hyped about stiffness, but not many are thinking too much about bearing drag. Then again, I suppose if the majority of non-racers truly cared enough about drag, we would be riding fared 'bents to pick up ~5Km/h, rather than trying to fit into the crowd with the latest piece of carbon with high-tech appeal.

There is a few posts on here by some bloke that lists crank lengths used by the peleton, they tend to be longerI have tried shorter cranks and for me I am slightly better on longer ones. I can hold a slightly higher cadence for the same resistence on my trainer work outs. My tt bike has 177.5 and the other roadie 175 but I don't have knee probs like you. The differnce is only small but my fastest tt times are all on the longer cranks, it is not huge by any means maybe some of it is placebo . Now that I have strava I'll be able to see on the hill climb segments what difference if any there is.

Good for you. Of course I was only stirring. I'll be interested to know the difference. Then to know for sure, you'd have to source a 53 for your compact and do it all again. Somehow I don't think that is going to happen though. I think TLL said his 180s made him faster too. It has been that well known for so long that I put 172.5 on my road bike in '93 for the same reason. Yes it's funny, but 172.5 is long for a guy who's ideal is supposed to be 165. The bike came with 170.

As someone else once said, it would be interesting to see a list of track cranks for the elite track riders. I would have thought if you are group racing instead of ITT that the ability to accelerate fast would be an advantage. Obviously from that list they don't seem to think it matters enough in the tours.

At this stage the difference is not much I am slightly faster up some of the climbs but haven't beaten times on others. The wind conditions or fitness probably makes more difference, it is small enough to be placebo. I feel better on the drops on the flat with the longer cranks and the small to big ring shifting is much better on the 130 bcd cranks so they are staying on.

warthog...ive just gone thru this exact same process with my S5 VWD... i took off the original FSA K-light BBright crank, and replaced it with my BB30 Quarq which has a S975 spider.

PM me if u need more info.... essentially for spacers on the non-drive side i have taken off all the BB30 adjuster and spacer, and replaced it with a wavy washer, and a ? 5 plus 1mm (grey) spacer. On the drive side ive used the ?11mm collar plas a ?3mm spacer. All fucntions well and chainline is in exacly the same position as the stock chainset. The Q factor on either side is also identical. I will confirm the spacer thicknesses tonight when i get home if u like....

Thanks Dr Mutley, I got it sorted with some advice off the Cervelo forums. Used the 11 mm spacer on the drive side, I can't remember if there was a grey rubber washer, if there was i'm pretty sure I used it. On the non drive I ended up using the grey rubber washer, 3 clear plastic spacers and the wave washer that came with the original crankset

A graph at the end of page 5 says I'd be better off with 160s for max power. I'm on 165s, so close enough.

That study from my quick read of it is for maximal power over a 30 sec sprint. That would correlate with sprinters tending toward shorter cranks. For sustained power I think longer cranks are better, got no studies though and there is probably bugger all in it.

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